NNNN.com actually is up. Sales are around $450-$600 recently compared with $350-$450 from sales last year. NNN.com is also up, check recent sales ($12k-$30k). Main driving factors appear to be the scarcity of these domains and the rapidly growing internet penetration in China, which is the main end-users of (and traffic for) numeric sites.

That said, I don't see NNNN.us having much value (except for great numbers), especially since the main value in numerics is in non-U.S. traffic.